Nonequilibrium spin current through interacting quantum dots

TL;DR

This paper presents a comprehensive theory for charge and spin currents in quantum dots with magnetic leads, accounting for interactions and noncollinear configurations, and explores the behavior near the Kondo regime.

Contribution

It introduces a method to explicitly separate equilibrium and nonequilibrium currents in interacting quantum dots with arbitrary magnetic configurations.

Findings

Spin current is enhanced near the Kondo regime due to interactions.

The theory can handle arbitrary local interactions and magnetic configurations.

Both equilibrium and nonequilibrium currents are expressed via the full retarded Green's function.

Abstract

We develop a theory for charge and spin current between two canted magnetic leads flowing through a quantum dot with an arbitrary local interaction. For a noncollinear magnetic configuration, we calculate equilibrium and nonequilibrium current biased by voltage or temperature difference or pumped by magnetic dynamics. We are able to explicitly separate the equilibrium and nonequilibrium contributions to the current, both of which can be written in terms of the full retarded Green's function on the dot. Taking the specific example of a single-level quantum dot with a large on-site Coulomb interaction, we calculate the total spin current near the Kondo regime, which we find to be generally enhanced in magnitude as compared to the noninteracting case.